Pass post type to count_user_posts() in get_the_author_posts();

[Caspie]

Prevents possible wrong posts count, return when no post type is passed - the default "post" is used. Related to the enhancement in #21364

[Caspie]

pass post type

[Caspie]

For cases when get_the_author_posts() is called and the current post is of a custom post type.

[tyxla]

Adding an assertion in the unit test Tests_User_Author::test_get_the_author_posts() that checks for the new $post->post_type parameter usage in the count_user_posts() call within get_the_author_posts().

[SergeyBiryukov]

In 31098:

Pass post type to count_user_posts() in get_the_author_posts().

props Caspie, tyxla.
fixes #30904.